The holdings climbed to $61.8 billion from $54.5 billion at the end of March, according to calculations by Bloomberg based on the central bank’s regulatory filing to the U.S. Securities and Exchange Commission and published on Wednesday. SNB spokesman Walter Meier declined to comment on the filing, which is the only detailed disclosure by the central bank of its equity portfolio.

Unlike some other big central banks, the SNB, led by President Thomas Jordan, holds equities as well as bonds. At the end of June, 20 percent of its 609 billion-franc ($628 billion) pile of foreign currencies was in stocks. The S&P 500 Index climbed 1.9 percent in the second quarter.

The SEC filing showed the institution had stakes in 2,581 companies listed in the U.S. Its biggest holdings were Apple Inc., Exxon Mobil Corp. and Microsoft Corp., according to data compiled by Bloomberg. It increased the number of shares it holds in all three companies over the quarter.

SNB officials, including Governing Board Member Andrea Maechler, have said repeatedly that they replicate broad-based indexes to serve the interest of monetary policy rather than to generate a profit. Some companies are excluded on ethical grounds. Maechler said in a speech in late March that the SNB doesn’t “actively engage in equity selection.”